The objective of this proposal is divided into four parts: 1. To investigate the possible co-ordination of silicon to the epoxide oxygen and its effect in the mode of ring-opening reactions of alpha, beta-epoxysilanes. 2. (a) To compare the stabilization of beta silyl cations with those of beta stannyl and beta germanyl cations (Me3Z-C-C+, Z = Si, Sn, Ge) (b) To compare their influence in the ring-opening reactions of their epoxides and to compare their beta-effect with the entropy effect in the cyclization reactions. (c) To study the anti-tumor activity of the lactones formed from the above reactions. 3. To investigate the mode of proton abstraction in Me3Si-CH2-CO-CH2-Ph, Me3Z-CH2-CH2-Ph, and Me3Si-CH2-CH2-ZMe3 where Z = Sn, and Ge. 4. To conduct theoretical studies using semi-empirical and ab initio calculations to obtain the calculated structures, energies, geometries, relative populations of anions and cations and compare the results with experimental data.